This invention relates to an apparatus for testing or measuring the slip resistance (static coefficient of friction) of surfaces such as floors, bathtubs and the like.
For example, industry standards are established for minimum friction coefficients that are acceptable in commercial flooring or bathtub interiors. In order to test such surfaces, these standards may be related, in the former case to the coefficient of friction as between the flooring surface and a material representative of a shoe sole, and in the latter case to the coefficient of friction as between the bath tub surface and a material representative of human skin simulating the sole of the foot. Further, it is desirable for testing purposes, to have apparatus available which can be readily transported from site to site in order to test floor, bathtub and like surfaces for slip resistance, rather than having to submit a surface sample to a laboratory for testing.
Over the years, numerous different machines have been proposed for testing surface friction or slip resistance. Applicant's prior U.S. Pat. No. 4,759,209, for example, incorporated herein by reference, discloses a portable test apparatus which includes an articulated linkage having at the bottom a foot plate with a foot pad of test material which rests on a surface to be tested, the apparatus including means for setting the linkage at selected angles and applying a load substantially instantaneously to the linkage at a selected angle to determine whether the pad will slip on the test surface at the selected angle.
The apparatus includes an upright frame carrying the articulated linkage, the frame being pivotally mounted on a base and being supported for movement along a part-circular segment disposed in a vertical plane. The frame is movable along the segment into selected angles to the vertical so as to pre-establish an angle of attack for the articulated linkage relative to the test surface. The top link of the articulated linkage comprises rods which extend through and project upwardly from the frame. A weight is carried at the top of the rods and a releasable trigger is provided between the top of the frame and the weight to hold the linkage with the foot pad slightly above a surface being tested in a slightly elevated position when the trigger is set and to substantially instantaneously allow the linkage to drop when the trigger is released. If the angle of the linkage is sufficiently shallow, the pad will slip on the test surface when the linkage is released. The trigger comprises an L-shaped lever, the horizontal limb of which is pivoted on the top of the frame. The top of the vertical limb engages the bottom of the weight when the trigger is set, and manually pivoting the lever disengages the vertical limb from the weight to release the trigger. Some effort is needed, however, to frictionally drag the top of the lever across the bottom surface of the weight to release the trigger.